Abstract
Water quality of Laguna de Bay, the largest lake in the Philippines, was survyed as a small joint survey of Japanese and Philippine NGO groups. The lake water had relatively high concentration of SS caused by resuspending silt and fine clay from the bottom sediment due to shallow water depth and strong wind. Chl a concentration was low in spite of high concentrations of nitrogen and phosphorus. Trihalomethane formation potential test showed high formation of bromine compounds due to intrusion of sea water into the lake. Relatively high concentration of SS, COD, nitrogen and phosphorus was observed at the mouth of the most polluted tributary.
